Near-field thermal transport between two identical twisted bilayer graphene sheets separated by a vacuum gap

Active control of heat flow is of both fundamental and applied interest in thermal management and energy conversion. Here, we present a fluctuational electrodynamic study of thermal radiation between twisted bilayer graphene (TBLG), motivated by its unusual and highly tunable plasmonic properties. We show that near-field heat flow can vary by more than 10-fold over only a few degrees of twist, and observe a larger variation with increasing chemical potential and decreasing temperature. Further, we identify special angles leading to heat flow extrema, which are dictated by the Drude weight in the intraband optical conductivity of TBLG, and are roughly linear with the chemical potential. As the twist angle decreases, we observe multiband thermal transport due to the increasing role of interband transitions, in analogy to monolayer graphene in a magnetic field. We also briefly discuss the effect of a small angular deviation and a substrate, which are experimentally relevant. Our findings are understood via the surface plasmons in TBLG, and highlight its potential for manipulating radiative heat flow.